The present invention is directed to improved pressure reducing and conditioning valves. Pressure reduction and conditioning valves have been developed to simultaneously reduce steam pressure and heat. Typically, pressure reducing and conditioning valves are utilized for precise temperature and pressure control in turbine by-pass, drying rolls, air preheater coils, unit tie lines, process reactors, fan drives, compressor drives, plant heating, fuel oil heating, evaporator supply, and atomizing steam.
Pressure reduction valves reduce the pressure of incoming steam. Steam conditioning valves operate by mixing superheated steam under high pressure with desuperheated steam or atomized water. A problem encountered with prior art pressure reducing and conditioning valves is that they are complex and difficult to control. A particular problem encountered with prior art conditioning valves was that conditioning occurs in proximity to the valve member. Such conditioning valves require complex structures to provide desuperheating steam or water directly into the valve member, and often failed to achieve uniform distribution of the atomized water or desuperheated steam. Prior art conditioning valves also accumulated condensate downstream of the valve members, and experienced water leakages. There has further been a need for conditioning and pressure reducing valves having trim diameters of approximately 1.0 to 2.0 inches. With the reduced trim diameter, the plug, stem and water outlet tube can be manufactured from a single piece, thereby facilitating manufacture and reducing cost.
In view of the above, it is an object of the present invention to provide pressure reducing and conditioning valves having trims with small enough diameters to permit the valve stem and plug to be fabricated from a single piece.
It is a further object of the present invention to provide pressure reducing and conditioning valve incorporating controlled steam leakage to heat the downstream side of the valve and to aid in the removal of condensate.
It is yet a further object of the present invention to provide pressure reducing and conditioning valves with improved water leakage control.
The present invention is directed to pressure reducing and conditioning valves having angled valve housings specifically designed to minimize thermal stresses and fatigue as well as to improve flow characteristics. Several embodiments of the invention incorporate an integral water proportioning system which supplies desuperheating water and which is designed to provide a fixed water to steam flow ratio proportional to the plug position and which is a function of the valve stroke. The invention further incorporates a system of labyrinths rather than piston rings. The labyrinth contains 6-10 grooves to reduce steam leakage between the trim and the bonnet for a balanced plug version. In addition, because of the reduced trim size, both plug and stem are manufactured out of a single piece.
The present invention, in its steam conditioning embodiments, incorporates a novel injection nozzle which uniformly distributes and atomizes the water within the high turbulence valve outlet area. The nozzle incorporates a swirling and accelerating chamber which helps to create a fine and consistent spray pattern. This feature assures complete atomization, and thereby optimizes evaporation and temperature control.